A known torque fluctuation absorber is provided on a drivetrain (i.e., a power transmission passage) between an engine and a motor generator (or a transmission) in a hybrid vehicle, for example, to thereby absorb or restrain torque fluctuations generated between the engine and the motor generator (or the transmission). Such torque fluctuation absorber may include a damper portion absorbing the torque fluctuations by means of an elastic force, a hysteresis portion absorbing or restraining the torque fluctuations by a hysteresis torque generated by friction, for example, and a limiter portion causing a slippage when the torque fluctuations are beyond absorbing capabilities of the damper portion and the hysteresis portion. Such torque fluctuation absorber is disclosed in JP2010-38312A (hereinafter referred to as Reference 1) including plural and individual damper portions so as to increase a torsion angle at each of the damper portions.
The damper portion generally absorbs the torque fluctuations caused by a torsion between an input rotation member and an output rotation member by means of a coil spring. In order to protect the coil spring from the excessive torsion between the input rotation member and the output rotation member, the damper portion includes a stopper portion so as to regulate the torsion between the input rotation member and the output rotation member. In a case where the torque fluctuation absorber includes the plural damper portions, the stopper portion is required at each of the plural damper portions. At this time, when the stopper portion is provided at a position radially displaced relative to a position where the coil spring is provided, the size in the radial direction of the torque fluctuation absorber may increase. In addition, when the stopper portion is provided at a position circumferentially displaced relative to the position where the coil spring is provided, the torsion angle of the damper portion may decrease.
A need thus exists for a torque fluctuation absorber which is not susceptible to the drawback mentioned above.